1. Field of the Invention
The present invention relates to a special anchor attachable to a wood roof understructure for securing a fall restraint lifeline.
2. Prior Art
Government regulations often require fall restraint or fall arrest systems for roofers. The most stringent regulations cannot always be met practically. For example, compliance with some regulations has required an anchor to which a lifeline is secured capable of withstanding 5,200 pounds of force without separation or structural failure. In common wood frame construction, application of a force of 5,200 pounds could tear apart the roof understructure. In such situations, compliance with the regulations was not possible. As a result, the regulations were not enforced and roofers often were not protected from injury due to falls.
Current regulations have more realistic specifications, such as a 4:1 ratio of anchor strength to roofer weight (including the usual load carried by the roofer) on a roof of moderate pitch. The anchor should withstand 1,120 pounds of force without failure, preferably about 1,200 pounds for a reasonable margin of safety, for a roofer weighing up to about 250 pounds carrying a load of up to about 30 pounds.
Despite the relaxation of government regulations, there is no known inexpensive, reliable, governmentally approved anchor which is easy to install such that it may be used safely in a practical fall restraint system for roofers in wood frame construction.
Glynn et al. U.S. Pat. No. 4,249,713, issued Feb. 10, 1981, discloses a specialized anchor formed of metal sheet material with long flat opposite end portions angled relative to each other to fit over the ridge of a roof understructure with holes for securing such end portions by nailing into aligned rafters at opposite sides of the ridge. The central portion of the anchor is return bent with registered holes for a snap hook to which a lifeline can be attached. At the end of the roofing procedure, Glynn et al. proposed that the central portion be bent over and covered by the ridge cap.
Jackson U.S. Pat. No. 3,237,717, issued Mar. 1, 1966, discloses a complicated safety rigging for roofers in which opposite ends of guidelines are anchored to the ground at opposite sides of a building structure.
Berry U.S. Pat. No. 742,565, issued Oct. 27, 1903, discloses a scaffold supported on an inclined roof by a "Z-shaped hook" which includes one leg hooked over the ridge of the roof.
Similarly, Elkins U.S. Pat. No. 677,645, issued Jul. 2, 1901, discloses a shingler's carriage suspended from special hinged hooks which are affixed to a roof at the ridge.